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Research & Scholarship

Current Research and Scholarly Interests

My research interests include studying the effects of obesity on anesthetic drug distribution, metabolism, and dose. I am using my expertise in pharmacogenomics, pharmacokinetics (PK), and pharmacodynamics (PD), to conduct research describing the effect of genotypic differences in obese subjects on drug distribution, metabolism, and effect. My current research interest is to examine the effect of insulin resistance and gene expression on the PK and PD of anesthetic drugs in obese subjects.

Clinical Trials

A High Resolution Pharmacokinetic/Pharmacodynamic Model of Propofol in Morbidly Obese SubjectsNot Recruiting

This study will determine how morbid obesity affects the distribution and metabolism of the
drug propofol. The investigators hypothesize that propofol will be distributed and
metabolized differently in morbidly obese subjects as compared to normal weight subjects.

Stanford is currently not accepting patients for this trial.For more information, please contact Jerry Ingrande, M.D., M.S., 650-723-7377.

The primary objective of this study is to determine the influence of insulin resistance on
drug metabolism and response in obese subjects. The investigators hypothesize that
expression of adiponectin (a hormone secreted by fat tissue), and specific variants in the
adiponectin gene can predict the insulin resistance and drug response among obese subjects.

Publications

Journal Articles

Abstract

Anesthesiologists are unique among most physicians in that they routinely use technology and medical devices to carry out their daily activities. Recently, there have been significant advances in medical technology. These advances have increased the number and utility of medical devices available to the anesthesiologist. There is little doubt that these new tools have improved the practice of anesthesia. Monitoring has become more comprehensive and less invasive, airway management has become easier, and placement of central venous catheters and regional nerve blockade has become faster and safer. This review focuses on key medical devices such as cardiovascular monitors, airway equipment, neuromonitoring tools, ultrasound, and target controlled drug delivery software and hardware. This review demonstrates how advances in these areas have improved the safety and efficacy of anesthesia and facilitate its administration. When applicable, indications and contraindications to the use of these novel devices will be explored as well as the controversies surrounding their use.

Abstract

The incidence and prevalence of adolescent obesity and adolescent heart failure are increasing, and anesthesiologists increasingly will encounter patients with both conditions. A greater understanding of the physiologic challenges of adolescent heart failure as they relate to the perioperative stressors of anesthesia and bariatric surgery is necessary to successfully manage the perioperative risks faced by this growing subpopulation. Here, we present a representative case of a morbidly obese adolescent with heart failure who underwent a laparoscopic bariatric operation and review the limited available literature on perioperative management in this age group. Specifically, we review evidence and offer recommendations related to preoperative evaluation, venous thromboembolism prophylaxis, positioning, induction, airway management, monitoring, anesthetic maintenance, ventilator management, and adverse effects of the pneumoperitoneum, rhabdomyolysis, and postoperative care.

Abstract

The unique anesthetic risks associated with the morbidly obese (MO) population have been documented. Pharmacologic management of these patients may be altered because of the physiologic and anthropometric changes associated with obesity. Unfortunately, studies examining the effects of extreme obesity on the pharmacology of anesthetics have been sparse. Although propofol is the induction drug most frequently used in these patients, the appropriate induction dosing scalar for propofol remains controversial in MO subjects. Therefore, we compared different weight-based scalars for dosing propofol for anesthetic induction in MO subjects.Sixty MO subjects (body mass index ?40 kg/m(2)) were randomized to receive a propofol infusion (100 mg · kg(-1) · h(-1)) for induction of anesthesia based on total body weight (TBW) or lean body weight (LBW). Thirty control subjects (body mass index ?25 kg/m(2)) received a propofol infusion (100 mg · kg(-1) · h(-1)) based on TBW. Syringe drop was used as the marker for loss of consciousness (LOC), at which point the propofol infusion was stopped. The propofol dose required for syringe drop and time to LOC were recorded.Total propofol dose (mg/kg) required for syringe drop and time to LOC were similar between control subjects and MO subjects given propofol based on LBW. MO subjects receiving a propofol infusion based on TBW had a significantly larger propofol dose and significantly shorter time to LOC. There was a strong relationship between LBW and total propofol dose received in all 3 groups.LBW is a more appropriate weight-based scalar for propofol infusion for induction of general anesthesia in MO subjects.

Abstract

Anaesthesiologists must be prepared to deal with pharmacokinetic and pharmacodynamic (PD) differences in morbidly obese individuals. As drug administration based on total body weight can result in overdose, weight-based dosing scalars must be considered. Conversely, administration of drugs based on ideal body weight can result in a sub-therapeutic dose. Changes in cardiac output and alterations in body composition affect the distribution of numerous anaesthetic drugs. With the exception of neuromuscular antagonists, lean body weight is the optimal dosing scalar for most drugs used in anaesthesia including opioids and anaesthetic induction agents. The increased incidence of obstructive sleep apnoea and fat deposition in the pharynx and chest wall places the morbidly obese at increased risk for adverse respiratory events secondary to anaesthetic agents, thus altering the PD properties of these drugs. Awareness of the pharmacology of the commonly used anaesthetic agents including induction agents, opioids, inhalation agents and neuromuscular blockers is necessary for safe and effective care of morbidly obese patients.

Abstract

Worldwide, the number of overweight and obese patients has increased dramatically. As a result, anesthesiologists routinely encounter obese patients daily in their clinical practice. The use of regional anesthesia is becoming increasingly popular for these patients. When appropriate, a regional anesthetic offers advantages and should be considered in the anesthetic management plan of obese patients. The following is a review of regional anesthesia in obesity, with special consideration of the unique challenges presented to the anesthesiologist by the obese patient.Recent studies report difficulty in achieving peripheral and neuraxial blockade in obese patients. For example, there is an increased incidence of failed blocks in obese patients compared with similar, normal weight patients. Despite difficulties, regional anesthesia can be used successfully in obese patients, even in the ambulatory surgery setting.Successful peripheral and neuraxial blockade in obese patients requires an anesthesiologist experienced in regional techniques, and one with the knowledge of the physiologic and pharmacologic differences that are unique to the obese patient.